n-Propyl bromide (NPB) is an article of commerce. It is useful for various applications including cold cleaning of electrical and mechanical parts. Depending upon the processing used in its manufacture, products containing at least 90 wt % of NPB and as high as about 98-99 wt % of NPB are available in the marketplace. The major impurities tend to be isopropyl bromide and 1,2-dibromopropane.
In order to gain widespread commercial acceptance, it is desired that the NPB product pass a 60° C. stability test developed by a Japanese company. This test requires that NPB be kept for 30 days in a 60° oven with its acidity remaining below 5 ppm (calculated as HBr). The test is carried out in a Teflon polymer capped 100 mL glass bottle filled to the shoulder with NPB and without excluding air. To successfully pass the 60° C. stability test, a suitable stabilizer system is deemed necessary as pure NPB can and does release HBr under the test conditions along with the release of propene. The ability of an NPB composition to pass this test, enables the composition to be stored and shipped without encountering any significant decomposition. Also, the recipient can utilize the composition for various operations conducted at modest temperatures such as cold cleaning of electrical and mechanical parts, again without fear of encountering significant decomposition.
Unstabilized NPB has desirable volatility characteristics for various cold cleaning applications. Thus a stabilizer system for NPB not only must be effective in preventing excessive acidity development during the 60° C. stability test, but in addition, preferably should not contribute to unacceptable residue formation upon evaporation of the NPB.